Field of the Invention
The present invention relates to a laser processing apparatus for performing laser processing to a workpiece such as a wafer.
Description of the Related Art
In a semiconductor device fabrication process, a plurality of crossing division lines are formed on the front side of a substantially disk-shaped semiconductor wafer to thereby define a plurality of separate regions where a plurality of semiconductor devices such as ICs and LSIs are each formed. The semiconductor wafer is divided along the division lines to thereby divide the regions where the semiconductor devices are formed from each other, thus obtaining a plurality of individual semiconductor device chips.
As a method of dividing a wafer such as a semiconductor wafer along the division lines, there has been proposed a method including the steps of applying a laser beam having an absorption wavelength to the wafer along the division lines to thereby form a laser processed groove as a break start point along each division line by ablation and next applying an external force to the wafer along each division line where the laser processed groove as the break start point is formed, thereby breaking the wafer along each division line.
The laser processing mentioned above is performed by using a laser processing apparatus. The laser processing apparatus includes workpiece holding means for holding a workpiece, laser beam applying means having a processing head for applying a laser beam to the workpiece held by the workpiece holding means, feeding means for relatively moving the workpiece holding means and the laser beam applying means in a feeding direction (X direction), indexing means for relatively moving the workpiece holding means and the laser beam applying means in an indexing direction (Y direction) perpendicular to the feeding direction (X direction), and alignment means for detecting a subject area of the workpiece to be processed (see Japanese Patent Laid-open No. 2006-289388, for example).